Rear caliper woes....

[timb]

Hi all, I'm having some struggles with my OSR caliper .. car is a 91 Eunos that I've had for a few months, so not fully aware of the service history although I know the PO changed pads regularly as he did a lot of track days etc., it's fitted with Skuzzle braided lines and filled with Motul RBF 600 fluid if that makes any difference!

Anyway, I noticed it was dragging 5mins into a drive at the weekend, so decided to see if I could sort it myself - never worked on disc brakes other than bleeding and adjusting the handbrake (although done the drums on my mini) so armed myself with a few youtube videos and the guide on here.

It seems the piston is stuck - the allen bolt adjuster is working in the sense that if I tighten it, I can't turn the hub by hand and when I loosen it I can but only with a fair bit of force so I guess it's only moving back a tiny bit. I've eliminated the handbrake lever being the culprit (I think?) by disconnecting the cable and checking the movement of the sprung lever - it springs back nicely to where it should be, and again if I pull on it with my fingers it locks the brake well. I've undone the brake fluid reservoir cap and also let a little fluid out of the bleeder valve to check it's not overly pressurised or having an issue returning fluid due to the flexi hose. I've got the bottom slide pin out no problem, but the caliper just won't swing up at all....what's the next step? I am thinking whacking it off with a hammer and drift, is that sensible or are there any other options?

Many TIA,

Tim

[Mazda Mender]

It sounds like there is more than one issue at fault here , the worm drive and the dry seized top slider pin.
If the worm drive is fudged , then its a new caliper, do not get the cheap Chinese rubbish as you will be throwing money away for a dangerous ill made copy, either new or refurbished from the likes of autolinkmx5.
Now as for the fused slider... It does not sound like the PO was doing all that he said bud, that means its fitted dry and water as gotten past the dust boot seal and its rust, you now need a good penetrating oil like plus gas "NOT WD40" , using the straw, lift the dust boot and spray under the dust boot towards the caliper and work it in up and down spraying as you go and with a lot of man grunts and swearing it should slowly free up and come off to be able to swap the caliper, you might need to help with a drift and hammer ,but you do need to be careful with where you whack, i'll get a pic to show you,Worste case is undo the carrier bolts and remove the whole thing from the upright.
Clean up the slider pin and invest in some red rubber grease and copper grease to be fitted correct and also with protection against this happening again.
But this is a case of not being done correct in the first place by the PO, so take what ever big ups they have said in a pinch of salts bud.
M-m

[timb]

Thanks Wayne, I've hit it with some plusgas this morning so lets see if I can get it to budge when I have a chance to look at this evening.

There was red grease on the bottom slider and I saw some on the top slider when I pulled back the boot to get the plusgas straw in, I do trust the PO that he did what he said, whether he did it correctly though is another matter!

[timb]

If the worm drive is fudged , then its a new caliper,

Hi Wayne, any reason why I couldn't fix it with a new wormdrive screw and piston (I'd do the seals at the same time)? Or is it just less hassle to replace the caliper completely?

[Mazda Mender]

Far easier to just replace it than the hassle of stripping it all down , by the time you have paid for the parts ,it's not far off the same price as a OE refurb.
M-m

[timb]

Far easier to just replace it than the hassle of stripping it all down , by the time you have paid for the parts ,it's not far off the same price as a OE refurb.
M-m

Well I got the caliper off now, slider pin looks ok so think it was just the piston holding it on, it's definitely not winding in/out apart from a very small amount....just put an order in with Andrew for a reconditioned one so hopefully I'll be back on the road soon

Thanks for all the advice, will make a donation shortly.

[GlennyGills]

Good work - well done.